Sure! Here's an example of a basic game implemented as a single HTML file, using JavaScript and enclosed in script tags. This game is a simple particle simulation where you can interact with the particles using your smartphone's touchscreen.
To play the game, open the HTML file in a web browser on your smartphone. As you touch the screen, particles will be created at the touched position and start moving around. The particles will bounce off the screen edges and continue to move until the game is closed.